The present invention relates to an isolated 18.3 kDa protein, DGP5p+, specific for Toxoplasma gondii, which contains a transmembrane protein. The present invention also relates to DGP5p protein which lacks the transmembrane protein of DGP5p+; recombinant DGP5p (rDGP5p) protein; and the nucleic acid sequences which encode these proteins. The RNA which encodes DGP5p and rDGP5p can be used to specifically identify T. gondii oocysts through RT-PCR. The isolated and recombinant proteins can be used as reagents to detect antibodies in the serum of infected individuals.
Toxoplasmosis, caused by the protozoan parasite Toxoplasma gondii, is one of the most common parasitic infections of man and other warm-blooded animals. It has been found worldwide from Alaska to Australia. Nearly one-third of humanity has been exposed to this parasite. In most adults it does not cause serious illness, but it can cause blindness and mental retardation in congenitally infected children and devastating disease in immunocompromised individuals (Dubey, J. P., and T. P. Beattie, Toxoplasmosis of animals and man, CRC Press, Boca Raton, Fla., 1988). Humans become infected by congenital transmission from mother to fetus, through ingestion of tissue cysts in under-cooked or uncooked meat, or by ingesting food or water contaminated with sporulated oocysts from infected feces (e.g., cat). Food animals, such as pigs, become infected by the same routes, resulting in meat products containing tissue cysts which could infect consumers. Currently, there are no tests which can differentiate between oocyst ingestion versus tissue cyst ingestion as the infection route. Development of such a test would make epidemiological studies possible to determine predominant infection routes, could lead to the development of fact-based strategies to reduce transmission, and could increase public perception of pork as a safe food product. Increased consumer awareness of the potential risks of acquiring T. gondii from fresh pork products represents a potentially serious problem for the U.S. pork industry. Food safety is a critical issue for the swine industry. Foodborne diseases are increasing in industrialized countries and consequently are more of a concern to consumers. Large outbreaks of foodborne diseases are being reported and covered extensively in the media, and the severe impact on children, the aged, and immunocompromised individuals has resulted in a heightened awareness of the consumer to the issue of contaminated food. Demands of consumers for pathogen free meat products have focused attention of government regulators and the meat industry on food safety, and the necessity to produce meat that is wholesome, safe and of high quality. Delivery of a safe product is essential for pork to remain a competitive commodity, both in the U.S. and globally.
Thus, there is a need for an agent useful for differentiating between oocyst versus tissue cyst induced T. gondii infection in humans and food animals.